Added the option removecr to inputs.exec to remove all carraige returns
(CR, ASCII 0x0D, Unicode codepoint \u0D, ^M). The option is boolean and
not enabled if not present in the config file.

closes #1606

Updated CHANGELOG.md with information about removecr

Ran go fmt ./...

Moved removal of CRs to internal/internal.go

Moved the code to remove carriage returns from
plugins/inputs/exec/exec.go to internal/internal.go. Additionally
changed the conditional on which it gets applied from using a
configuration file option to checking if it is running on Windows.

Moved Carriage Return check to correct place

Moved the carriage return removal back to the exec plugin. Added unit
testing for it. Fixed a bug (removing too many characters).

Ran go fmt ./...

Reverted CHANGELOG to master

Updated Changelog

Allow using glob pattern in the command list in configuration. This enables for
example placing all commands in a single directory and using /path/to/dir/*.sh
as one of the commands to run all shell scripts in that directory.

Glob patterns are applied on every run of the commands, so matching commands can
be added without restarting telegraf.

closes #1142

closes #762

This constitutes a large change in how we will parse different data
formats going forward (for the plugins that support it)

This is working off @henrypfhu's changes.

closes #637

closes #613

With HTTP JSON or Elasticsearch, one can also process values nested in arrays.